Diskus is a high-level hard drive diagnostic and limited repair tool. It checks the disk geometry by writing numbered IDs into the sectors of the hard drive. Later one can verify that these sector-IDs on the disk are still correct, thereby detecting data which was not correctly written. There is an option to "freshen" the data on your harddrive, which will read and rewrite the sectors. With modern drives this will re-map defective sectors.
md5chk is a tool for creating MD5 sums. It was designed so that its output would be easy to use with command line shells. It guarantees that the MD5 sum is always "clean" of characters that would be misinterpreted by the shell and that special characters in the file names are always properly escaped.
tunerlimit is a preload library that allows some fine-tuning of when calls to setrlimit(2) are allowed, and when they are "blocked". This can be useful in situations where, for example, SELinux policies cause programs to fail completely when making trivial or idempotent calls to setrlimit().
The Middleman System (mdm) is a set of utilities that help you parallelize your shell scripts. Its design is based on ideas from superscalar computer processors: it fetches commands as your script is running, detects potential interference between commands on the fly, and issues commands for execution in parallel as appropriate.
Secrond is a light-weight cron implementation that allows running of user-specified programs at periodic scheduled times, handling tasks in intervals of seconds rather than minutes, as well as hours and days. While it is possible to achieve similar behavior by using a traditional cron daemon and adding calls to sleep() to the programs executed, it is impractical.